give someone the once-over
Also, give someone the eye. Look or stare at someone with interest. For example, The new coach gave the team the once-over before introducing himself, or He gave her the eye and she blushed. The first expression, a colloquialism, generally implies a quick but comprehensive survey or assessment. The variant, a slangy usage sometimes amplified to give the glad eye, often signifies an inviting glance. [Early 1900s] Also see make eyes at.